Construction of support columns in soil



Aug. 22, i967 R. E. LANDAU CONSTRUCTION OF SUPPORT COLUMNS IN SOIL Filed Nov. 21, w63

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INVENTOR. RICHARD E. LANDAU United States Patent O 3,336,760 CONSTRUCTION F SUPPORT COLUMNS v IN SOIL Richard E. Landau, 6161 Dry Harbor Road, Middle Village, N.Y. 11379 Filed Nov. 21, 1963, Ser. No. 325,478 7 Claims. (Cl. 61-53.6)

The present invention relates to a novel construction method and, more particularly, to a novel method of installing columns of supporting material, such as, caissons, piers and footings, in soils.

In the support of heavy structures, it is often necessary to extend the foundation support to a deep soil stratum, such as, rock or the like, which is capable of supporting heavy load concentrations to minimize the possibility of foundation deection and failure. This lis generally accomplished by the driving or otherwise inserting of one ormore elongated supports called piles into the soil until the tips or point-s thereof rest or bear on the support stratum. The structure foundation is then placed on the pile tops. However, where very heavy foundation loads are anticipated, the number of piles and their relative spacing to prevent overload or overstress of the support stratum might be unfeasible or undesirable.

Usually, it is not possible to drive piles closer than two to three feet on centers without adverse eiect. In such instances, large diameter caissons or piers are employed. Such caissons resemble the piles; however, they are of much larger diameter. Caissons may be of uniform diameter calle-d straight shaft caissons, or the lower end thereof may be enlarged or belled-out, forming a pedestal to increase the bearing area thereof on the support stratum. Caissons thus permit a decrease in the number of foundation supports and an increase in their relative spacing without increasing the unit stress of the support stratum.

In the case of the pedestal caisson, a relatively small diameter support at the surface supports a relatively heavy load without adverse effect. Further, the volume of concrete saved thereby is considerable. However, heretofore, the costs of constructing such pedestal caisson piles have also been considerable, off-setting any savings in costs of concrete.

Likewise, where, as in underwater locations and the like, that is, locations where the construction .is below the water table, ordinary methods of installing caissons cannot be economically employed, caissons, either of uniform diameter or belled, are employed. In such underwater environments, it may also be necessary to pressurize the caisson-s.

Caissons have heretofore generally utilized a shell, casing, mandrel or other elongated hollow container. In one method, called the Chicago method, the caissons are formed by successively excavating the caisson hole for a short distance, and sheeting and bracing the sides of the hole to form the container. This method, of course, is generally unfeasible for underwater sites.

In Aanother method, the container is preformed and successively driven down a short way in advance of the excavation, and excavate-d by hand, or, if the caisson is of sufficiently large diameter, by machine; for example, a clamshell. In yet another method, the container is a hollow shell sunk to supporting stratum by hand excavation, with the earth and Water being hel-d back from filling the shell by compressed air. In this case, the method is slow, complicated and dangerous, and extreme care has to be taken during construction. This latter method is usually employed for underwater caisson construction.

Other methods have attempted to avoid the use of hand excavation by employingrspecial apparatus, such as, special excavating drills and shell driving devices, all without universal success. As an example, the dry-process rotary excavating machine utilizes a cutting tool to excavate, but requires a lining to be placed in sections to support the cavity so formed.

To form the belled caisson, usually the container has to be pressurized when the work is below water or the soil is not self-supporting. In any event, a man has to be inserted through the container down to the support lstratum where the pedestal or bell was hand excavated by digging or drilling, depending on the type of stratum encountered. Apparatus to form the bell mechanically have not always proved satisfactory. This same procedure also has to be followed in the event that a preformed shell is Ibeing placed, and is blocked by an obstruction, such as, a boulder or rock, as it is being driven down to the support stratum.

It will be at once evident that the foregoing procedures are not only tedious, time-consuming and costly, but, likewise, may be dangerous. I have found a substantially simpler way land more economical manner of installing all such foundation supports in soil, which method can be employed with only minor variations in all types of soils irrespective of ground water conditions. My method also eliminates the need for using separate cavity support or container means for the caisson.

Broadly, the method for forming the caisson involves helically cutting into the soil, utilizing a ilight auger to penetrate and Where necessary segmentally support the soil, removing all or part of the soil within the cavity by either conveying such soil along the auger ights which in instances need not be continuous, or else containing the soil within the auger flights and partially or fully removing the soil supported by said flights with the removal of the auger, and backlling the cavity so formed with suitable material or materials as necessary for the required foundation construction.

FIG. 1 is a cross-sectional view of `apparatus illustrating the method of carrying out one form of the embodiment of the present invention. FIG. 2 is a crosssectional view of apparatus illustrating the method of carrying lout a second form of the embodiment of the present invention. The embodiments of the present invention illustrated in FIG. 1 and FIG. 2 are not to be construed as limiting the invention, as other forms will -be evident to those familiar in the art.

FIG. 1 and FIG. 2 illustrate two forms of the embodiment of the invention whereby a suppor-t column is formed in soil by means of a flight auger F consisting of a shaft 1 with projecting flights 2.,The flight auger F is penetrated into the soil 4 to a desired depth 5. Forward rotation of the auger F with controlled advance develops a core of earth 9 contained within the flights 2 and bounded by the exterior of shaft 1. Withdrawing of the auger F from the soil 4 by pulling and controlling its reverse rotation, a cavity periphery 6 is formed by virtue of soil 11 left in place, see FIG. 1. In this embodiment, backiill material 3 normally placed substantially simultaneously with the formation of the cavity periphery 6; however, in specific instances of cavity self-support, backll material 3 may be placed subsequent to cavity formation. By pulling the auger F without rotation in a reverse direction, a cavity 8, FIG. 2, may be formed having a peripheral dimension substantially equal to that of the auger flight 2. By rotating the auger F in a reverse direction and pulling the auger at a rate -of one pitch length per rotation, then a cavity 7 may be formed having a peripheral dimension substantially equal to that of shaft 1, FIG. 2. Withdrawal of the auger F from the soil 4 at the rate of one pitch length per revolution may result in the formation of crevices 10 which reect lthe dimensions of flight 2, FIG. 2. The placing of backll material into cavities 7 and 8, FIG. 2, will complete the formation of the support column for this embodiment of the invention. If crevices 10 do not close of themselves under the stress of the auger operation, the crevices 10 may become filled with backfill material. Such crevices are not detrimental to the support column, and will eventually close or become filled with soil if not initially by the backfill material. By controlling the rate of reverse rotation of the Iauger F and the rate of pulling from the soil 4, the dimension of the cavity periphery 6 and the final support column configuration can be varied in dimension, limited only by the outside diameter of auger flight 2.

Should a straight shaft caisson be required, it can be produced in either of two ways. One involves helically cutting into the soil, with the external diameter of the auger flights defining the periphery of the cavity formed as the auger is extracted from the ground and backfilling simultaneously upon withdrawal with concrete or other desired caisson material.

In lthe second manner, a hollow shaft auger is employed, such that the internal diameter of the hollow auger shaft is the equivalent of the outside diameter of the caisson formed and the auger flights serve only as a means of cutting into the soil. After the auger hollow shaft is placed at the full depth by helically cutting into the soil, concrete is placed into the shaft and left in the soil as the auger is retracted by reversing its rotation, thereby leaving the soil contained within its flights in the ground.

In either method, any surplus soil excavated which approximately represents the volumn of the formed shaft would remain either at the ground surface or be otherwise left in the ground, depending upon the soil type involved and the rate of withdrawal of the auger with respect to its rotation. If the rate of withdrawal approximates one pitch length per revolution, then substantially all the soil within the flights would effectively be entirely left in the ground. If the rate of withdrawal were less than one pitch length per revolution, some compactive eiort would be effected on the soil with the result that some additional soil would be conveyed by the flights from the ground surface to a point below the ground. If the rate were greater than one pitch length per revolution, then the cavity would be somewhat enlarged requiring more concrete backlill. Preferably, I advocate withdrawing the auger at `about one pitch length per revolution.

Where a pedestal caisson is required, the auger is first penetrated, as heretofore, to the required depth, as, for example, to the support stratum. The auger is then withdrawn, either fully or in stages, to the desired bell or pedestal height. This forms a cavity in the soil substantially equal in diameter to the outside diameter of the auger flights. Depending on the support characteristics of the soil, such cavity may be simultaneously backfilled with concrete or the like as by using the hollow shaft auger. If the soil is sufficiently self-supporting, such cavity can be backfilled subsequent to this partial withdrawal.

Further, if desired, subsequent to or simultaneously with the partial withdrawal of the auger, the cavity may be temporarily supported, even where the soil is not entirely self-supporting, by introducing thereinto a supporting medium such as compressed air. This would permit, among other things, the entry of a man into the cavity to perform any manual operations or inspections that were required. This would be especially desirable in underwater locations where the man must work below the water level. In such case, the hollow au-ger shaft can be put under air pressure, and a man can be placed therein through a suitable lock which can be part of, adjoining, or otherwise used in conjunction with the auger at a point accessible from the ground surface.

To form the main smaller-diameter portion of the caisson, the auger is reverse rotated as it is being removed as heretofore described for one method of forming the straight-shafted caisson or pier. Here, again, if conditions require, this smaller-diameter shaft can be simultaneously backfilled as through the hollow shaft auger or, if conditions allow, the entire length, or any portion thereof, of the cavity can be backfilled subsequent to withdrawal of the auger.

By varying the rate of withdrawal and rotation, it is possible, if desired, to form a tapered transition from the bell to the pier shaft. The latter, however, is not considered necessary, as the volume of concrete saved lby this procedure would be relatively small for most applications of the method.

Where a hollow shaft auger is employed and the caisson is to be installed in an underwater location, or where the water table is high, the water in the soil or surrounding environment may be kept out of the excavation by employing a suitable cap therefor. Further, if obstructions lare encountered as the auger is advancing, such obstructions may be penetrated by utilizing a suitable cutting head for the auger, or by inserting a suitable cutting unit, such as a rock drill, through the hollow shaft. Likewise, where it is desirable to have a man enter into the excavation, the auger hollow shaft should be of a sufficiently large diameter to permit passage to its full depth. Such entry may be required to install equipment, for inspection purposes, or to effect removal or destruction of an obstruction either by hand or Iby means of the auger equipment. If the obstruction size is larger than the auger, such that its removal leaves a void larger than desired, the soil can be conveyed downward and compacted by reversing the auger rotation direction, thereby filling the cavity with soil from the auger flights and then continuing the caisson installation as before.

One form of apparatus suitable for use in carrying out the method of the present invention is disclosed in my co-pending application, Ser. No. 246,411, filed Dec. 21, 1962, now U.S. Patent No. 3,303,656, using a substantially continuous flight auger.

Although certain particular embodiments of the invention are herein disclosed for purposes of explanation, further modifications thereof, after study of the specification, will be apparent to those skilled in the art to which the invention pertains. Reference should accordingly be had to the appended claims in determining the scope 0f the invention.

What is claimed and desired to be secured by Letters Patent is:

1. The method of forming an elongated pedestal support column in soil, comprising penetrating said soil to the desired soil depth by helically cutting thereinto with -a flight auger, pulling the auger from the soil to a selected height, thereby forming a first cavity in said soil defined substantially by the youter diameter of the flights of said auger, removing the auger completely from said soil by reversing the direction of helical cutting of said auger to form a second cavity in said soil communicating with said first cavity and defined substantially by the outer diameter of the auger shaft, and backfilling said cavities with columnar material to form said pedestal support in said soil, said soil having the capacity to substantially sustain itself against collapse prior to the completion of the backfill operation.

2. The method of claim 1, wherein the auger flight is substantially continuous.

3. The method of claim 1, wherein said auger is hollow-shafted, and wherein said columnar material is concrete, and at least said first cavity is filled with concrete through said hollow shaft.

4. The method lof forming columnar supports in soil, comprising penetrating said soil to the desired soil depth by helically cutting thereinto with a flight auger, removing said auger to thereby form a cavity in said soil, in-

troducing a gaseous support medium into said cavity for temporarily maintaining said cavity prior to fully removing said auger from said soil, and backiilling said cavity with the columnar material to form said column.

5. The method -of forming an elongated pedestal support column in soil, comprising penetrating said soil to the desired soil depth by helically cutting thereinto with a Hight auger, removing the auger completely from said soil by withdrawing the auger from the soil to a selected height thereby forming a first cavity in said soil substantially dened by the -outer diameter of the flights of said auger, backlling said Iirst cavity with columnar material, reversing the direction of helical cutting of said auger to form a second cavity in said soil communicating with said first cavity and substantially dened by the outer diameter of the auger shaft, backlling said second cavity with columnar material to form said column support.

6. The method `of claim 5 wherein the formation of the rst cavity is effected by pulling the auger and controlling its -reverse rotation whereby said cavity is formed with a varying diameter.

7. The method of forming an elongated pedestal support column in soil, comprising penetrating said soil to the desired soil depth by helically cutting thereinto with a ight auger, pulling the auger from the soil to a selected height thereby forming a irst cavity in said soil substantially defined by the outer diameter of the iiights of said auger, withdrawing the auger completely from said soil by reversing the direction of helical cutting of said auger to form a second cavity in said soil communicating with said first cavity and substantially defined by the outer diameter of the auger shaft, introducing a support medium into at least said irst cavity for maintaining at least said rst cavity, and backlling said cavities with columnar material to for-m said pedestal support.

References Cited UNITED STATES PATENTS 1,605,722 10/ 1926 Rotinoi 6l-53.62 2,729,067 1/1956 Patterson 61-53.58 2,791,886 5/1957 Veder 61-35 2,805,553 9/1957 Allard 6l-53.64 X 2,920,455 1/ 1960 Ryser et al. 61-53.64 3,191,390 6/1965 Schutte 61-53.52 X 3,200,599 8/ 1965 Phares et al 6l-53.64 3,206,936 9/1965 Moor 61-53.64

DAVID J. WILLIAMOWSKY, Primary Examiner.

JACOB L. NACKENOFF, JACOB SHAPIRO,

Examiners. 

1. THE METHOD OF FORMING AN ELONGATED PEDESTAL SUPPORT COLUMN IN SOIL, COMPRISING PENETRATING SAID SOIL TO THE DESIRED SOIL DEPTH BY HELICALLY CUTTING THEREINTO WITH A FLIGHT ANGER, PULLING THE AUGER FROM THE SOIL TO A SELECTED HEIGHT, THEREBY FORMING A FIRST CAVITY IN SAID SOIL DEFINED SUBSTANTIALLY BY THE OUTER DIAMETER OF THE FLIGHTS OF SAID AUGER, REMOVING THE AUGER COMPLETELY FROM SAID SOIL BY REVERSING THE DIRECTION OF HELICAL CUTTING OF SAID AUGER TO FORM A SECOND CAVITY IN SAID SOIL COMMUNICATION WITH SAID FIRST CAVITY AND DEFINED SUBSTANTIALLY BY THE OUTER DIAMETER OF THE AUGER SHAFT, AND BACKFILLLING SAID CAVITIES WITH COLUMNAR MATERIAL TO FORM SAID PEDESTAL SUPPORT IN SAID SOIL, SAID SOIL HAVING THE CAVITY TO SUBSTANTIALLY SUSTAIN ITSELF AGAINST COLLAPSE PRIOR TO THE COMPLETION OF THE BACKFILL OPERATION. 